In turbofan engines, the air entering the turbomachine is divided into a primary flow or hot flow passing through a compressor which supplies a combustion chamber arranged downstream and into a secondary flow or cold flow, providing a considerable portion of the thrust, which flows around the compressor and which is discharged with the hot gases.
In order to restrict the consumption of fuel and the noise level, the engine manufacturers seek to increase the rate of dilution which is equal to the ratio between the output flow of cold air and the output flow of hot air, which leads to an increase in the diameter of the turbomachine. Because these engines are installed under the wings, the increase in the rate of dilution is limited by the need to have a minimal distance between the nacelle, that is to say the outer envelope of the turbomachine, and the ground.
For safety reasons, the engine is usually positioned upstream of the wing in order that, in the event of a shattering of a rotor disk, for example, the debris is prevented from reaching the portions of the wing where the fuel is stored. For the same reason, the engines are not incorporated into the wing.
A first approach would consist in increasing the height of the landing gear in order to increase the distance between the turbomachine and the ground. However, this solution is not satisfactory because it leads to a substantial increase in the cost and weight of the aircraft. A second approach consists in bringing the turbomachine closer to the wing and therefore reducing the distance between the nacelle and the wing. The air circulating in this space is thus accelerated, which may cause the formation of shock waves inducing a considerable increase in aerodynamic drag.
It is however preferred, in the prior art, to maintain a sufficient ground clearance and bring the engine closer to the wing, despite the disadvantages that that comprises.